Involvement of hypoxia-inducible factor-1α in the oxidative stress induced by advanced glycation end products in murine Leydig cells

The Impact of Diabetes on Male Silkworm Reproductive Health

The increasing prevalence of diabetic reproductive complications has prompted the development of innovative animal models. The use of the silkworm Bombyx mori as a model for diabetic reproductive damage shows potential as a valuable research tool. This study employed silkworms as a novel model to investigate diabetic reproductive damage. The silkworms were fed a high-glucose diet containing 10% glucose to induce a diabetic model. Subsequently, the study concentrated on assessing the influence of diabetes on the reproductive system of male silkworms. The results indicate that diabetes resulted in reduced luteinizing hormone (LH) and testosterone (T) levels, as well as elevated triglyceride (TG) levels in male silkworms. Moreover, diabetes mellitus was associated with pathological testicular damage in male silkworms, accompanied by decreased glutathione peroxidase (GSH-Px) and superoxide dismutase (SOD) levels, along with increased malondialdehyde (MDA) levels in the testis. Additionally, diabetes mellitus reduced the expression of siwi1 and siwi2 genes in the testis of male silkworms. Overall, these results support using silkworms as a valuable model for studying diabetic reproductive damage.

Pathogenesis of diabetic complications: Exploring hypoxic niche formation and HIF-1α activation

Hypoxia is a common feature of diabetic tissues, which highly correlates to the progression of diabetes. The formation of hypoxic context is induced by disrupted oxygen homeostasis that is predominantly driven by vascular remodeling in diabetes. While different types of vascular impairments have been reported, the specific features and underlying mechanisms are yet to be fully understood. Under hypoxic condition, cells upregulate hypoxia-inducible factor-1α (HIF-1α), an oxygen sensor that coordinates oxygen concentration and cell metabolism under hypoxic conditions. However, diabetic context exploits this machinery for pathogenic functions. Although HIF-1α protects cells from diabetic insult in multiple tissues, it also jeopardizes cell function in the retina. To gain a deeper understanding of hypoxia in diabetic complications, we focus on the formation of tissue hypoxia and the outcomes of HIF-1α dysregulation under diabetic context. Hopefully, this review can provide a better understanding on hypoxia biology in diabetes.

Paternal determinants of early embryo development

Existing research has primarily focused on investigating the impacts of the maternal environment, female fertility phenotype, and genetics on pregnancy loss in dairy cattle. Recently, attention has been directed toward understanding the role the sire has on embryo quality and viability. Studies have shown there is a paternal influence on early pregnancy loss, but the specific mechanisms impacting pregnancy establishment and maintenance remain unclear. Despite clear differences that sires have on pregnancy outcomes, there is a lack of evidence regarding specifically how sires influence pregnancy. Sperm characteristics, such as motility, concentration, and morphology, have been extensively studied, but further research is needed to understand what makes one sire more or less fertile than another sire and how this affects pregnancy. To effectively address pregnancy loss, a deeper understanding of the processes involved from fertilisation to blastocyst formation is essential, particularly for understanding early pregnancy loss.

Diabetes-Induced Autophagy Dysregulation Engenders Testicular Impairment via Oxidative Stress

Testes produce sperms, and gamete generation relies on a proper niche environment. The disruption of hierarchical regulatory homeostasis in Leydig or Sertoli cells may evoke a sterile phenotype in humans. In this study, we recapitulated type 2 diabetes mellitus by using a high-fat diet- (HFD-) fed mouse model to identify the phenotype and potential mechanism of diabetes-induced testicular impairment. At the end of the study, blood glucose levels, testosterone structure, testicular antioxidant capacity, and testosterone level and the expression of hypoxia-inducible factor- (HIF-) 1α, apoptosis-related protein cleaved-caspase3, and autophagy-related proteins such as LC3I/II, p62, and Beclin1 were evaluated. We found that long-term HFD treatment causes the development of diabetes mellitus, implicating increased serum glucose level, cell apoptosis, and testicular atrophy (P < 0.05 vs. Ctrl). Mechanistically, the results showed enhanced expression of HIF-1α in both Sertoli and Leydig cells (P < 0.05 vs. Ctrl). Advanced glycation end products (AGEs) were demonstrated to be a potential factor leading to HIF-1α upregulation in both cell types. In Sertoli cells, high glucose treatment had minor effects on Sertoli cell autophagy. However, AGE treatment stagnated the autophagy flux and escalated cell apoptosis (P < 0.05 vs. Ctrl+Ctrl). In Leydig cells, high glucose treatment was adequate to encumber autophagy induction and enhance oxidative stress. Similarly, AGE treatment facilitated HIF-1α expression and hampered testosterone production (P < 0.05 vs. Ctrl+Ctrl). Overall, these findings highlight the dual effects of diabetes on autophagy regulation in Sertoli and Leydig cells while imposing oxidative stress in both cell types. Furthermore, the upregulation of HIF-1α, which could be triggered by AGE treatment, may negatively affect both cell types. Together, these findings will help us further understand the molecular mechanism of diabetes-induced autophagy dysregulation and testicular impairment, enriching the content of male reproductive biology in diabetic patients.

MiR-125b attenuates retinal pigment epithelium oxidative damage via targeting Nrf2/HIF-1α signal pathway

The retinal pigment epithelium cells (RPE) are sensitive to oxidative stimuli due to long-term exposure to various environmental stimuli. Thus, the oxidative injury of RPE cells caused by the imbalance of redox homeostasis is one of the main pathogenic factors of age-related macular degeneration (AMD). But the sophisticated mechanisms linking AMD to oxidative stress are not fully elucidated. Activation of Nrf2 signal pathway can protect RPE cells from oxidative damage. The present study investigated the regulating mechanism of miR-125b in Nrf2 cascade and evaluated its antioxidant capacity. The in vitro studies indicated that overexpression of miR-125b substantially inhibited Keap1 expression, enhanced Nrf2 expression and induced Nrf2 nuclear translocation. Importantly, functional studies demonstrated that forced expression of miR-125b could significantly elevate cell proliferation and superoxide dismutase (SOD) levels while reduce reactive oxygen species (ROS) overproduction and malondialdehyde (MDA) formation. Further studies showed that miR-125b had no effect when Nrf2 was silenced in ARPE-19 cells. Additionally, the results identified that Nrf2 silence induced ROS accumulation enhances HIF-1α protein expression, while miR-125b could offset this effect via promoting HIF-1α protein degradation. Subsequent in vivo studies demonstrated that sodium iodate induced outer retina thinner was reversed with exogenous supplementation of miR-125b, which was cancelled in Nrf2 knockout mice. In conclusion, this study illustrated that miR-125b can protect RPE from oxidative damage via targeting Nrf2/HIF-1α signal pathway and potentially may serve as a therapeutic agent of AMD.

Icariin improves testicular dysfunction via enhancing proliferation and inhibiting mitochondria-dependent apoptosis pathway in high-fat diet and streptozotocin-induced diabetic rats

BACKGROUND

Diabetes mellitus (DM), a chronic metabolic disease, severely impairs male reproductive function. However, the underpinning mechanisms are still incompletely defined, and there are no effective strategies or medicines for these reproductive lesions. Icariin (ICA), the main active component extracted from Herba epimedii, is a flavonoid traditionally used to treat testicular dysfunction. Whether ICA can improve male reproductive dysfunction caused by DM and its underlying mechanisms are still unclear. In this study, by employing metformin as a comparative group, we evaluated the protective effects of ICA on male reproductive damages caused by DM and explored the possible mechanisms.

METHODS

Rats were fed with a high fat diet (HFD) and then intraperitoneally injected with streptozotocin (STZ) to induce diabetes. Diabetic rats were randomly divided into T2DM + saline group, T2DM + metformin group and T2DM + ICA group. Rats without the treatment of HFD and STZ were used as control group. The morphology of testicular tissues was examined by histological staining. The mRNA expression levels were determined by quantitative real-time PCR. Immunostaining detected the protein levels of proliferating cell nuclear antigen (PCNA), hypoxia-inducible factor 1-alpha (HIF-1α) and sirtuin 1 (SIRT1) in testicular tissues. TUNEL assay was performed to determine cell apoptosis in the testicular tissues. The protein expression levels of HIF-1α and SIRT1 in the testicular tissues were determined by western blot assay.

RESULTS

ICA effectively improved male reproductive dysfunction of diabetic rats. ICA administration significantly decreased fasting blood glucose (FBG) and insulin resistance index (IRI). In addition, ICA increased testis weight, epididymis weight, sperm number, sperm motility and the cross-sectional area of seminiferous tubule. ICA recovered the number of spermatogonia, primary spermatocytes and Sertoli cells. Furthermore, ICA upregulated the expression of PCNA, activated SRIT1-HIF-1α signaling pathway, and inhibited intrinsic mitochondria dependent apoptosis pathway by upregulating the expression of Bcl-2 and downregulating the expression of Bax and caspase 3.

CONCLUSION

These results suggest that ICA could attenuate male reproductive dysfunction of diabetic rats possibly via increasing cell proliferation and decreasing cell apoptosis of testis. ICA potentially represents a novel therapeutic strategy against DM-induced testicular damages.

Effects of exposure to methylglyoxal on sperm motility and embryonic development after fertilization in mice

Methylglyoxal (MG) is a precursor for the generation of endogenous advanced glycation end-products involved in various diseases, including infertility. The present study evaluated the motility and developmental competence after in vitro fertilization of mouse sperm which were exposed to MG in the capacitation medium for 1.5 h. Sperm motility was analyzed using an SQA-V automated sperm quality analyzer. Intracellular reactive oxygen species (ROS), membrane integrity, mitochondrial membrane potential, and DNA damage were assessed using flow cytometry. The matured oocytes were inseminated with MG-exposed sperm, and subsequently, the fertilization and embryonic development in vitro were evaluated in vitro. The exposure of sperm to MG did not considerably affect the swim-up of sperm but resulted in a deteriorated sperm motility in a concentration-dependent manner, which was associated with a decreased mitochondrial activity. However, these effects was not accompanied by obvious ROS accumulation or DNA damage. Furthermore, MG diminished the fertilization rate and developmental competence, even after normal fertilization. Collectively, a short-term exposure to MG during sperm capacitation had a critical impact on sperm motility and subsequent embryonic development after fertilization. Considering that sperm would remain in vivo for up to 3 days until fertilization, our findings suggest that sperm can be affected by MG in the female reproductive organs, which may be associated with infertility.

RACK1 mediates the advanced glycation end product-induced degradation of HIF-1α in nucleus pulposus cells via competing with HSP90 for HIF-1α binding

Hyperglycemia can drive advanced glycation end product (AGE) accumulation and associated nucleus pulposus cell (NPC) dysfunction, but the basis for this activity has not been elucidated. Hypoxia-inducible factor-1α (HIF-1α) is subject to cell-type-specific AGE-mediated regulation. In the current study, we assessed the mechanistic relationship between AGE accumulation and HIF-1α degradation in NPCs. Immunohistochemical staining of degenerated nucleus pulposus (NP) samples was used to assess AGE levels. AGE impact on NPC survival and glycolysis-related gene expression was assessed via 3-(4,5)-dimethylthiazol(-z-y1)-3,5-di-phenyltetrazolium bromide assay and quantitative reverse-transcription polymerase chain reaction (qRT-PCR), while HIF-1α expression in NPCs following AGE treatment was monitored via Western blot analysis and qRT-PCR. Additionally, a luciferase reporter assay was used to monitor HIF-1α transcriptional activity. The importance of the receptor for activated C-kinase 1 (RACK1) as a mediator of HIF-1α degradation was evaluated through gain- and loss-of-function experiments. Competitive binding of RACK1 and HSP90 to HIF-1α was evaluated via immunoprecipitation. Increased AGE accumulation was evident in NP samples from diabetic patients, and AGE treatment resulted in reduced HIF-1α protein levels in NPCs that coincided with reduced HIF-1α transcriptional activity. AGE treatment impaired the stability of HIF-1α, leading to its RACK1-mediated proteasomal degradation in a manner independent of the canonical PHD-mediated degradation pathway. Additionally, RACK1 competed with HSP90 for HIF-1α binding following AGE treatment. AGE treatment of NPCs leads to HIF-1α protein degradation. RACK1 competes with HSP90 for HIF-1α binding following AGE treatment, resulting in posttranslational HIF-1α degradation. These results suggest that AGE is an intervertebral disc degeneration risk factor, and highlight potential avenues for the treatment or prevention of this disease.

The Role of Transforming Growth Factor-Beta in Retinal Ganglion Cells with Hyperglycemia and Oxidative Stress

A characteristic of diabetes mellitus is hyperglycemia, which is considered with an emphasis on the diabetic retinopathy of progressive neurodegenerative disease. Retinal ganglion cells (RGCs) are believed to be important cells affected in the pathogenesis of diabetic retinopathy. Transforming growth factor-beta (TGF-β) is a neuroprotective protein that helps to withstand various neuronal injuries. To investigate the potential roles and regulatory mechanisms of TGF-β in hyperglycemia-triggered damage of RGCs in vitro, we established RGCs in 5.5, 25, 50, and 100 mM D-glucose supplemented media and focused on the TGF-β-related oxidative stress pathway in combination with hydrogen peroxide (H₂O₂). Functional experiments showed that TGF-β1/2 protein expression was upregulated in RGCs with hyperglycemia. The knockdown of TGF-β enhanced the accumulation of reactive oxygen species (ROS), inhibited the cell proliferation rate, and reduced glutathione content in hyperglycemia. Furthermore, the results showed that the TGF-β-mediated enhancement of antioxidant signaling was correlated with the activation of stress response proteins and the antioxidant pathway, such as aldehyde dehydrogenase 3A1 (ALDH3A1), heme oxygenase-1 (HO-1), nuclear factor erythroid 2-related factor (Nrf2), and hypoxia-inducible factor (HIF-1α). Summarizing, our results demonstrated that TGF-β keeps RGCs from hyperglycemia-triggered harm by promoting the activation of the antioxidant pathway, suggesting a potential anti-diabetic therapy for the treatment of diabetic retinopathy.

Advanced glycation end products enhance macrophage polarization to the M1 phenotype via the HIF-1α/PDK4 pathway

Atherosclerotic plaque rupture followed by luminal thrombosis is recognized as the main cause of acute cardiovascular events, especially in patients with diabetes. Although previous studies identified stimulation of macrophages polarization with advanced glycation end products (AGEs) results in the rapid progression of atherosclerosis, the underlying mechanisms are not understood fully. The purpose of this study was to investigate the effect of hypoxia-inducible factor-1α (HIF-1α) and pyruvate dehydrogenase kinase 4 (PDK4), critical proteins for regulating glucose metabolism, on macrophages polarization in diabetic atherosclerosis, and relevant mechanisms involved. We found that there is an increased number of M1 macrophages in carotid atherosclerotic tissues of diabetic mice and in AGE-bovine serum albumin (BSA)-treated RAW264.7 cells. Furthermore, we observed that HIF-1α was upregulated in AGE-BSA-induced M1 polarization and that the HIF-1α knockdown reduced macrophage polarization to M1 phenotype caused by AGE-BSA via regulation of PDK4. Thus, our study identified the critical role of HIF-1α/PDK4 axis in AGE-BSA-induced M1 polarization, which reflected the potential association between energy metabolism and inflammation in macrophages.

The role of advanced glycation end products in human infertility

Advanced glycation end products (AGEs) are heterogeneous products of the non-enzymatic interaction between proteins and reducing sugars. Numerous studies have shown that AGEs are associated with senescence, diabetes, vascular disease, aging and kidney disease. Infertility has been affected approximately 10 to15% of couples of reproductive ages. AGEs accumulation has been shown to play a crucial role in pathogenesis of infertility-related diseases. The present review provides the generation process, mechanism and pathological significance of AGEs and the novel treatment targeting AGEs for infertility.

Lycium barbarum Polysaccharides Improve Testicular Spermatogenic Function in Streptozotocin-Induced Diabetic Rats

The objective of this study was to investigate the protective effects of Lycium barbarum polysaccharides (LBP) on testicular spermatogenic function in streptozotocin (STZ)-induced diabetic rats. Compared to the control group, blood glucose levels were significantly increased and the insulin resistance was markedly aggravated in STZ-induced diabetic rats. Further, the weight of testis and epididymis and the sperm number and motility were decreased in diabetic rats. Pathological changes were also observed in the spermatogenic tubules, along with a decreased number of spermatogenic cells, downregulated proliferating cell nuclear antigen (PCNA) expression, and increased cell apoptosis in the testes. Compared to the saline-treated diabetic rat group, metformin and LBP treatment significantly decreased the level of blood glucose and improved insulin resistance and testicular function. After treatment with metformin and LBP, the pathological changes in the spermatogenic tubules improved significantly, with an increase in the number of spermatogenic cells, upregulation of PCNA, and suppression of apoptosis in the testes. The expressions of sirtuin 1 (SIRT1) and hypoxia-inducible factor 1-alpha (HIF-1α) in diabetic testes were also upregulated by metformin or LBP treatment. In summary, LBP exerted protective effects by increasing cell proliferation, inhibiting cell apoptosis, and regulating SIRT1/HIF-1α expression in the testes of diabetic rats.

HIF-1α/PDK4/autophagy pathway protects against advanced glycation end-products induced vascular smooth muscle cell calcification

Osteogenic differentiation of VSMC is one of the main causes of diabetic vascular calcification, and AGEs accumulation accelerates the calcification of VSMCs in diabetic patients. Autophagy has also been found to play an important role in the process of vascular calcification. However, the potential link between AGEs, autophagy and vascular calcification is still unclear and was investigated in this study. Primary VSMCs were isolated from the thoracic aorta of Sprague Dawley rats and cultured with AGEs-BSA to induce osteogenic differentiation. VSMCs calcification was evaluated by measuring the calcium content, RUNX2 protein levels, and by Alizarin red S staining. We demonstrated that treatment of VSMCs with AGE-BSA increased the expression of HIF-1α and PDK4. AGE-BSA treatment increased LC3-II and decreased p62 protein levels. AGE-BSA exposure enhanced autophagic flux determined by mRFP-GFP-LC3 adenovirus, induced co-localization of LC3-II and LAMP-1, and increased the number of autophagasome under TEM. HIF-1α/PDK4 pathway was activated during AGEs-induced autophagy of VSMCs. In addition, autophagy played a protective role during AGE-induced calcification of VSMCs. In conclusion, AGEs enhance autophagy via the HIF-1α/PDK4 signaling pathway, and autophagy helps attenuate AGE-induced calcification of VSMCs.

Protective effects of catalpol on diabetes mellitus-induced male reproductive damage via suppression of the AGEs/RAGE/Nox4 signaling pathway

AIMS

Diabetes mellitus (DM)-induced reproductive damage is an important cause of infertility for male DM patients, we herein evaluated the effects of catalpol on diabetic reproductive damage through the suppression of the AGEs/RAGE/Nox4 signaling pathway.

METHODS

KK-Ay diabetic reproductive damage mice were administered with catalpol for 8 weeks, the testis/body weight ratio, testicular histopathology, the levels of endogenous hormone and the activity of testicular marker enzymes were determined. In vitro, the GC-2 cell injury model was induced by advanced glycation end-products (AGEs) and pretreated with catalpol. Cell viability, apoptosis, and oxidative stress markers were detected and the mechanism based on the AGEs/RAGE/Nox4 pathway was explored.

KEY FINDINGS

Catalpol showed remarkable capacity on protecting diabetic reproductive damage by improving the histomorphology of the testes, increasing the testis/body weight ratio and activity of acid phosphatase (ACP), lactate dehydrogenase (LDH), gamma-glutamyl transferase (γ-GT). The reduced testosterone (T), luteinizing hormone (LH) and follicle-stimulating hormone (FSH) levels in DM mice were also reversed with catalpol intervention. Moreover, catalpol showed markedly effects of anti-oxidative in vivo and in vitro, which significantly down-regulated reactive oxygen species (ROS) levels and restored superoxide dismutase (SOD) activity, meanwhile decreased GC-2 cell apoptosis and Bax/Bcl-2 ratio. Moreover, the over-expression of receptors for AGEs (RAGE), NADPH oxidase type 4 (Nox4) and phosphorylation of nuclear transcription factor-κB p65 (NF-κB p65) were suppressed by catalpol.

SIGNIFICANCE

Catalpol could alleviate DM-induced male reproductive damage by inhibiting oxidative stress-induced apoptosis and inflammation mediated by AGEs/RAGE/Nox4 signaling pathway.

Reduced Glycolysis Contributed to Inhibition of Testis Spermatogenesis in Rats After Chronic Methamphetamine Exposure

BACKGROUND Previous reports suggested that methamphetamine (METH) exposure could lead to inhibition of rat testis spermatogenesis. Glycolysis and glucose metabolism as well as oxidative stress have been implicated in testis spermatogenesis. Here we explored the underlying mechanism of local metabolism and glycolysis of testis after METH exposure. MATERIAL AND METHODS METH was intraperitoneally injected into rats with different doses and duration of METH exposure to establish short-term and chronic exposure models. The serum 8-hydroxy-2 deoxyguanosine (8-OHdG) level of rats was detected by enzyme-linked immunosorbent assay. Untargeted gas chromatography-mass spectrometry analysis was applied to identify differential metabolites and metabolic signature. The mRNA expression of hypoxia inducible factor 1alpha (HIF1alpha), glucose transporter 1 (GLUT1), hexokinase 1 (HK1) and lactate dehydrogenase C (LDHC) in rat testes were detected by polymerase chain reaction. Further, we determined the 4 proteins with western blotting and immunohistochemistry. RESULTS Decreased testes index and sperm counts were showed in the chronic METH group. The metabolome revealed that the main differential metabolites impacted were associated with glycolysis and glucose metabolism. The mRNA and protein expression of GLUT1, HK1, and LDHC were reduced in the chronic METH group but elevated in the short-term METH group, whereas HIF1alpha was upregulated in the short-term METH group but remained at baseline in the chronic METH group. CONCLUSIONS Overall, glucose metabolism was regulated by HIF1alpha after short-term METH exposure. Reduced glycolysis in the testis led to impaired spermatogenesis after chronic METH exposure.

Alpha-lipoic acid suppresses Nε-(carboxymethyl) lysine-induced epithelial mesenchymal transition in HK-2 human renal proximal tubule cells

N^ε-(carboxymethyl) lysine (CML) plays causal roles in diabetic complications. In the present study, we investigated whether CML-induced HIF-1α accumulation and epithelial-mesenchymal transition (EMT) in HK-2 renal proximal tubular epithelial cells. Treatment with CML-BSA increased reactive oxygen species (ROS) production reduced the mitochondrial membrane potential and induced mitochondrial fragmentation. Pre-treatment of cells with antioxidant, α-lipoic acid, normalised the ROS production and restored the mitochondrial membrane potential. These changes were accompanied with morphological changes of epithelial mesenchymal transition. CML-BSA increased the protein level of hypoxia-inducible factor-1α (HIF-1α), and the EMT-associated transcription factor, TWIST. These effects were reversed by α-lipoic acid. CML-BSA increased the protein levels of mesenchymal-specific markers, including vimentin, α-smooth muscle actin, which were alleviated by pre-treatment with α-lipoic acid. Our data suggest that CML-BSA induces EMT through a ROS/HIF-1α/TWIST-dependent mechanism, and that α-lipoic acid may alleviate the CML-induced EMT in renal tubular cells.

Investigating the Glycating Effects of Glucose, Glyoxal and Methylglyoxal on Human Sperm

Glycation is the non-enzymatic reaction between reducing sugars, such as glucose, and proteins, lipids or nucleic acids, producing Advanced Glycation End (AGE) products. AGEs, produced during natural senescence as well as through lifestyle factors such as diet and smoking, are key pathogenic compounds in the initiation and progression of diabetes. Importantly, many of these factors and conditions also have influence on male fertility, affecting sperm count and semen quality, contributing to the decreasing trend in male fertility. This study investigated the impact of AGEs on sperm damage. In vitro sperm glycation assays were used to determine the levels and localization of the potent AGE compound, carboxymethyl-lysine (CML) in response to treatment with the glycating compounds glucose, glyoxal and methylglyoxal. Sperm function assays were then used to assess the effects of glycation on motility and hyaluronan binding, and levels of oxidative DNA damage were analyzed through measurement of the marker, 8-oxoguanine. Results showed that glyoxal, but not glucose or methylglyoxal, induced significant increases in CML levels on sperm and this correlated with an increase in 8-oxoguanine. Immunocytochemistry revealed that AGEs were located on all parts of the sperm cell and most prominently on the head region. Sperm motility and hyaluronidase activity were not adversely affected by glycation. Together, the observed detrimental effects of the increased levels of AGE on DNA integrity, without an effect on motility and hyaluronidase activity, suggest that sperm may retain some fertilizing capacity under these adverse conditions.

Matrine-Type Alkaloids Inhibit Advanced Glycation End Products Induced Reactive Oxygen Species-Mediated Apoptosis of Aortic Endothelial Cells In Vivo and In Vitro by Targeting MKK3 and p38MAPK Signaling

Background

The matrine‐type alkaloids are bioactive components extracted from Sophora flavescens, which is used in treatment of diabetes mellitus in traditional Chinese medicine. Advanced glycation end products mediate diabetic vascular complications. This study was aimed to investigate the protective effects and molecular mechanisms of matrine‐type alkaloids on advanced glycation end products–induced reactive oxygen species–mediated endothelial apoptosis.

Methods and Results

Rats aorta and cultured rat aortic endothelial cells were exposed to advanced glycation end products. Matrine‐type alkaloids, p38 mitogen‐activated protein kinase (MAPK) inhibitor, and small interference RNAs against p38 MAPK kinases MAPK kinase kinase (MKK)3 and MKK6 were administrated. Intracellular reactive oxygen species production, cell apoptosis, phosphorylation of MKKs/p38 MAPK, and expression levels of heme oxygenase/NADPH quinone oxidoreductase were assessed. The nuclear factor erythroid 2‐related factor 2 nuclear translocation and the binding activity of nuclear factor erythroid 2‐related factor 2 with antioxidant response element were also evaluated. Matrine‐type alkaloids suppressed intracellular reactive oxygen species production and inhibited endothelial cell apoptosis in vivo and in vitro by recovering phosphorylation of MKK3/6 and p38 MAPK, nuclear factor erythroid 2‐related factor 2 nuclear translocation, and antioxidant response element binding activity, as well as the expression levels of heme oxygenase/NADPH quinone oxidoreductase. p38 MAPK inhibitor treatment impaired the effects of matrine‐type alkaloids in vivo and in vitro. MKK3/6 silencing impaired the effects of matrine‐type alkaloids in vitro.

Conclusions

Matrine‐type alkaloids exert endothelial protective effects against advanced glycation end products induced reactive oxygen species–mediated apoptosis by targeting MKK3/6 and enhancing their phosphorylation.

Hypoxia driven glycation: Mechanisms and therapeutic opportunities

Tumor masses are deprived of oxygen and characterized by enhanced glucose uptake followed by glycolysis. Elevated glucose levels induce non-enzymatic glycosylation or glycation of proteins which leads to accumulation of advanced glycation end products (AGE). These AGE molecules bind to their respective receptors called the receptor for advanced glycation end products (RAGE) and initiate several aberrant signaling pathways leading to onset of diseases such as diabetes, Alzheimer's, atherosclerosis, heart failure and cancer. The role of AGE in cancer progression is being extensively studied in recent years. As cancer cells are hypoxic in nature and adapted to glycolysis, which induces glycation, its effects need to be understood in greater detail. Since AGE-RAGE signaling is involved in cancer progression, inhibition of AGE-RAGE interaction could be a potential therapeutic target. The purpose of this review is to highlight the role of AGE-RAGE interaction in hypoxic cancer cells.